Display device comprising multifunction glass, production method, and optical element having a Fresnel structure

Abstract

A display device including a holding device that can be placed on the head of a user, an image generating module fixed to the holding device and generating an image, and a multifunction glass that is fixed to the holding device and has a coupling in area and a coupling out area. The image produced is coupled into the multifunction glass via the coupling in area, guided in the multifunction glass to the coupling in area, and extracted via the coupling out area, in such a way that the user can perceive the coupled out image superimposed on the surroundings when the holding device is placed on the head of the user. The coupling in area has a Fresnel structure causing a folding of the beam path when the image is injected into the multifunction glass, said structure having an imaging property.

The invention claimed is: 
     
       1. A display device, comprising
 a holding device structured to be fittable onto the head of a user; 
 an image-generating module which generates an image and is attached to the holding device, and 
 a multifunction optical element including a coupling-in area and a coupling-out area attached to the holding device, wherein the generated image is coupled into the multifunction optical element via the coupling-in area, guided in the multifunction optical element to the coupling-out area and coupled out via the coupling-out area such that when the holding device is fitted onto the head the user can perceive the coupled-out image superimposed on surroundings, wherein the coupling-in area comprises a Fresnel structure which brings about a folding of the beam path during the coupling of the image into the multifunction optical element and has an imaging property, and wherein the Fresnel structure has several Fresnel segments, wherein optically effective facets of the Fresnel segments optically correspond to an imaginary optical effective surface which is curved and has neither mirror symmetry with relation to a center plane nor rotational symmetry with relation to a center axis. 
 
     
     
       2. The display device according to  claim 1 , wherein the Fresnel structure is formed at a material boundary surface of the multifunction optical element. 
     
     
       3. The display device according to  claim 2 , wherein the material boundary surface at which the Fresnel structure is formed is a curved material boundary surface. 
     
     
       4. The display device according to  claim 1 , wherein the Fresnel structure is formed to be reflective. 
     
     
       5. The display device according to  claim 1 , further wherein the optical effective surface has no translational symmetry. 
     
     
       6. The display device according to  claim 1 , wherein a maximum height of each facet is substantially the same. 
     
     
       7. The display device according to  claim 1 , wherein a shape of the facets is an approximation of a shape of the corresponding surface section of the imaginary effective surface. 
     
     
       8. The display device according to  claim 7 , wherein the shape of the facets is a linear approximation of the shape of the corresponding surface section of the imaginary effective surface. 
     
     
       9. The display device according to  claim 1 , wherein the facets are curved concavely in cross-section. 
     
     
       10. The display device according to  claim 1 , wherein the facets are curved convexly in cross-section. 
     
     
       11. The display device according to  claim 1 , wherein the Fresnel segments are directly neighbouring. 
     
     
       12. The display device according to  claim 1 , wherein the Fresnel segments are spaced apart from each other. 
     
     
       13. A method of producing a multifunction optical element of a display device, comprising:
 forming a Fresnel structure which has an imaging property as well as a folding property for the beam path in a coupling-in area of the multifunction optical element by forming the Fresnel structure to have several Fresnel segments and forming optically effective facets of the Fresnel segments such that the optically effective facets optically correspond to an imaginary optically effective surface which is curved and has neither mirror symmetry with relation to a center plane nor rotational symmetry with relation to a center axis. 
 
     
     
       14. The method according to  claim 13 , further comprising forming the Fresnel structure on a curved material boundary surface of the multifunction optical element. 
     
     
       15. The method according to  claim 13 , further comprising forming the Fresnel structure such that the corresponding imaginary optically effective surface has no translational symmetry. 
     
     
       16. The method according to  claim 13 , further comprising producing the multifunction optical element on the basis of production data which are generated computationally by dividing an optical model surface into several height regions and computationally arranging the surface sections of the individual height regions or approximations of the surface sections at a base surface such that surface sections optically correspond to the optically effective surface. 
     
     
       17. The method according to  claim 16 , further comprising arranging the surface sections or the approximations of the surface sections computationally at a curved base surface. 
     
     
       18. An optical element, comprising:
 an optically effective surface which at least in part has a Fresnel structure with several Fresnel segments, 
 wherein optically effective facets of the Fresnel segments optically correspond to an imaginary optical effective surface which is curved and has no mirror symmetry with relation to a center plane nor rotational symmetry with relation to a center axis.